Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) What:		/sys/firmware/devicetree/*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) Date:		November 2013
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) Contact:	Grant Likely <grant.likely@arm.com>, devicetree@vger.kernel.org
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) Description:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) 		When using OpenFirmware or a Flattened Device Tree to enumerate
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) 		hardware, the device tree structure will be exposed in this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) 		directory.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) 		It is possible for multiple device-tree directories to exist.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) 		Some device drivers use a separate detached device tree which
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) 		have no attachment to the system tree and will appear in a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) 		different subdirectory under /sys/firmware/devicetree.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) 		Userspace must not use the /sys/firmware/devicetree/base
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) 		path directly, but instead should follow /proc/device-tree
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) 		symlink. It is possible that the absolute path will change
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) 		in the future, but the symlink is the stable ABI.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) 		The /proc/device-tree symlink replaces the devicetree /proc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) 		filesystem support, and has largely the same semantics and
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 		should be compatible with existing userspace.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) 		The contents of /sys/firmware/devicetree/ is a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) 		hierarchy of directories, one per device tree node. The
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) 		directory name is the resolved path component name (node
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) 		name plus address). Properties are represented as files
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) 		in the directory. The contents of each file is the exact
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) 		binary data from the device tree.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) What:		/sys/firmware/fdt
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) Date:		February 2015
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) KernelVersion:	3.19
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) Contact:	Frank Rowand <frowand.list@gmail.com>, devicetree@vger.kernel.org
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) Description:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 		Exports the FDT blob that was passed to the kernel by
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) 		the bootloader. This allows userland applications such
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) 		as kexec to access the raw binary. This blob is also
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) 		useful when debugging since it contains any changes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) 		made to the blob by the bootloader.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) 		The fact that this node does not reside under
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) 		/sys/firmware/device-tree is deliberate: FDT is also used
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) 		on arm64 UEFI/ACPI systems to communicate just the UEFI
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) 		and ACPI entry points, but the FDT is never unflattened
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) 		and used to configure the system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) 		A CRC32 checksum is calculated over the entire FDT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) 		blob, and verified at late_initcall time. The sysfs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) 		entry is instantiated only if the checksum is valid,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) 		i.e., if the FDT blob has not been modified in the mean
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) 		time. Otherwise, a warning is printed.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) Users:		kexec, debugging